Heraldic/vexillological work: More than 100 publications (most of
them on vexillological topics, but also on heraldry and on Hausmarken,
house signs). His main publication is the Vor- und Frühgeschichte des
europäischen Flaggenwesens [hor71];
other vexillological publications are about the war ensign of 1921, flags
of the old Reich, the flag of the Teutonic Order, flags of Oldenburg,
Helgoland, Kniphausen, Münster, Arensberg, Trier, Dortmund, Soest,
Münster, and the East Frisian colors.